Precast Concrete Sandwich Panels Research Articles

Experimental Analysis of the Mechanical Behavior of Shear Connectors for Precast Sandwich Wall Panels When Subjected to the Push-Out Tests

Precast concrete sandwich panels consist of two outer layers connected by a central connector and an inner insulating layer that enhances thermal and acoustic performance. A key challenge with these panels is eliminating thermal bridges caused by metallic connectors, which reduce energy efficiency. PERFOFRP connectors, made from perforated glass fiber-reinforced polymer (GFRP) sheets, have been proposed to address this issue. These connectors feature holes that allow concrete to pass through, creating anchoring pins that enhance shear resistance and prevent the separation of the concrete layers. This research aimed to evaluate the effect of the diameter and number of holes on the mechanical strength of PERFOFRP connectors. Three diameters not previously reported in the literature were selected: 12.70 mm, 15.88 mm, and 19.05 mm. A total of 18 specimens, encompassing 6 different configurations with varying numbers of holes, underwent push-out tests. The most significant resistance increase was a 15% gain over non-perforated connectors, observed in the configuration featuring three holes of 19.05 mm. The connections exhibited rigid and nearly linear behavior until failure.

Structural performance of precast concrete sandwich panels with bolt-steel plate connection subjected to axial loading

A new precast concrete sandwich panel with glass fiber-reinforced polymer connectors was proposed, utilizing bolt-steel plate connections. A compressive experiment was carried out to investigate the performance. The main damage was concrete crushing in the bolt connection region, at the panel bottom, and above the joint. The connector type, solid concrete rib, slenderness ratio, and thickness affected the failure mode and bearing capacity. The use of GFRP connectors and solid concrete ribs enhanced the ultimate bearing capacity and stiffness of the panels while reducing the lateral deflection. Higher slenderness ratios leading to reduced axial bearing capacity and increased lateral deflection. Finally, the results of the existing empirical calculation formulae were compared with experimental ones, and they were overly conservative. A new formula for predicting the bearing capacity was proposed, and the difference percentages between the proposed formula and experimental results were −0.4 %–2.8 %, which was the most accurate prediction formula.

Experimental and numerical investigations on the axial compression performance of precast geopolymer concrete sandwich wall panel

This paper investigated a novel precast concrete sandwich panel (PCSP) which made by the geopolymer concrete and enabled by the glass fiber reinforced polymer (GFRP) hexagonal tube connector. Six precast geopolymer concrete sandwich wall panel (PGCSP) specimens were fabricated and tested under axial compression load. The investigating parameters included the connector spacing, panel height, and panel thickness. The failure mode, axial load capacity, load-axial deflection relationship, and load-concrete strain relationship were studied and discussed. Moreover, two-dimensional (2D) finite-element (FE) analysis was conducted to reproduce the test. Parameter analysis was then performed to modify the axial load capacity formula in the Chinese code GB50010-2010. The results indicated that: all specimens exhibited large eccentric compression failure due to the second-order effect, which was caused by concrete crushing and horizontal cracking in the two wythes, respectively; with the decrease of the connector spacing, the crushing area of the specimens would be enlarged, the out-of-plane lateral deformation would be decreased, and the axial load capacity decreased by 17 % and 42 % when the connector spacing changed from 300 mm to 600 mm and 900 mm, respectively; with the decrease of the panel height and the increase of concrete wythes thickness, the axial load capacity of the specimens almost presented a linear increase; the established 2D FE model and the modified formula effectively reflected the axial load capacity of the specimens.

Experimental and Numerical Investigation on the Behaviour of Precast Concrete Sandwich Panels with Different Shear Connectors

Experimental and Numerical Investigation on the Behaviour of Precast Concrete Sandwich Panels with Different Shear Connectors

Experimental and numerical study on the shear performance of stainless steel-GFRP connectors for use in precast concrete sandwich panels

Precast Concrete Sandwich Panel (PCSP) is composed of concrete load-bearing panels, thermal insulation panels, and decorative panels, which are assembled through connectors, integrating load-bearing, thermal insulation, and decorative functions. The connector bears the main shear force between the wall panels, and the shear resistance and insulation performance of the connector largely determine the mechanical stability and insulation effect of the wall panels, which is a key component in PCSPs. The current common practice is to cross assemble stainless steel insulation (SSI) connectors and Glass-Fiber-Reinforced Plastic (GFRP) connectors into PCSPs, which can reduce building energy consumption and save resources while meeting strength and insulation requirements. A large-scale pull-out test on a PCSP with intersecting SSI-GFRP connectors was conducted in this paper. The damage process and damage pattern of PCSP were observed and the shear performance of SSI-GFRP connectors was analyzed. Secondly, a numerical analysis model of the test PCSP was built using ABAQUS finite element software and its validity was verified through the test data. In addition, parameters such as connector diameter, connector number ratio and concrete strength were analyzed for their effect on the shear performance of SSI-GFRP connectors and it was found that connector diameter and connector number ratio had a significant effect. Finally, it is found that there are some differences between the classical theory for calculating the shear performance of SSI-GFRP connectors and the actual results. A theoretical correction factor (ζ) is given to improve the accuracy of the calculation of the classical theory, and its influencing factors and changing rules are investigated.

Optimization of Shear Resistance in Precast Concrete Sandwich Wall Panels Using an S-Type Shear Connector

Precast concrete sandwich wall panels (PCSPs) are popular for building exteriors due to their high thermal efficiency, composite performance, and low manufacturing and maintenance costs. Researchers have investigated the possibility of reducing the panel thickness while maintaining the cladding components’ thermal efficiency and strength to further improve efficiency and to reduce material consumption. However, limited research has been conducted on the shear bonding of steel plates, which is critical to ensuring durability and energy efficiency. This study investigated the shear behaviour of PCSPs with an S-type shear connector (SSC) through nine push-off tests and non-linear finite element modelling using Abaqus. Parametric studies were carried out to investigate the influence of the geometric properties of the SSC, the yield strength of the steel and the insulation thickness. The results suggest that the maximum secant stiffness for SSCs was achieved at a width of 101.4 mm and a thickness of 2 mm. Therefore, it is recommended that the width of the SSCs be limited to this value or less. Furthermore, the study found that increasing the yield strength of the steel beyond a thickness of 2 mm and a width of 101.4 mm did not improve the results and had a negative impact on the secant stiffness of the SSCs.

In-plane shear performance and damage evolution of FRP connectors for composite sandwich panels

This study investigated the in-plane shear responses of four types of connectors (single-strand truss, double-strand truss, grid-type, and I-shaped) in precast concrete sandwich panels (PCSPs). The influence of connector type, connector arrangement, and wythe material on the shear performance was discussed through in-plane shear tests and finite element analysis. The failure modes and test results of the four types of connectors were closely related to their shear resistance mechanisms. Changing the connector arrangement method from continuous along the length to discrete arrangement improved connector damage extent and toughness index (TI). The substitution of ordinary concrete with ECC or UHPC in wythes can prevent the wythes failure and enhance peak load (Pm). The finite element (FE) model using the Hashin damage model and randomly generated fibers can accurately capture the shear response of the connectors within PCSP. The damage factor was introduced for quantitative analysis of the damage processes in connectors and wythes and corresponding damage evolution model was developed. Furthermore, the damage evolution model was applied to characterize the degradation of shear stiffness in the load-slip curve, and a load-slip theoretical model that accounted for the progressive development of damage was established.

Advancements in precast concrete sandwich panels for load bearing structures

Concrete sandwich panels consist of two concrete layers separated by an insulating foam core, offering thermal insulation, structural strength, and fire resistance. This study investigates sustainable precast concrete sandwich panels made with industrial waste materials like limestone slurry, quarry waste, and basalt fiber as shear connectors. The research evaluates the flexural and axial strength behavior of these panels and explores strategies to improve their structural performance. The panels were fabricated with outer concrete layers, an expanded polystyrene (EPS) insulation core, and basalt fiber connectors. Flexural tests using four-point bending and axial compression tests were conducted on panels with varying concrete layer thicknesses and basalt fiber widths. Findings revealed panels with thicker outer concrete layers (35mm) and wider basalt fiber connectors (11.5mm) exhibited higher cracking loads, load-hardening behavior, and increased ductility compared to thinner layers and narrower connectors. The axial test showed premature failure at the top and bottom quarters. Thicker concrete layers and wider basalt fiber connectors enhanced crack control, load distribution, and ductile behavior under flexural loading. Strengthening measures like additional reinforcement, proper anchorage detailing, and increased shear reinforcement at the end regions are recommended to improve axial load-bearing capacity and prevent premature end failures. The PCSP demonstrated up to 40% cost savings over commercial products while providing better thermal insulation than conventional brick masonry due to the EPS core. Overall, the study promotes developing sustainable, energy-efficient, and cost-effective load-bearing sandwich panel systems.

Seismic behavior of horizontally spliced single-side superposed shear wall using a concealed column

The single-side superposed (SSS) shear wall is an innovative precast concrete sandwich panel that better meets the requirements of building industrialization. However, the seismic behavior of SSS shear walls remains inadequately understood. In this paper, a full-scaled horizontally spliced SSS shear wall using a concealed column and an integral SSS shear wall of the same dimensions were tested. The seismic behavior was investigated considering various aspects including hysteresis performance, bearing capacity, ductility performance, energy dissipation capacity, and stiffness degradation curve. The simulation models were established by the Abaqus, which provided the verification and further research for the test. Furthermore, two innovative splicing forms were proposed to optimize the existing specimens through the Abaqus. The experimental results indicated that implementing the vertical joint would lead to a decrease in the yield-bearing capacity by 24%, but it would also enhance the ultimate bearing capacity by 12.7%. Meanwhile, the deformation capacity would improve by 9.7%. The numerical simulations demonstrated that the suggested splicing methods effectively meet the demands of building industrialization.

Flexural Behavior of a New Precast Insulation Mortar Sandwich Panel

This article introduces the experimental and analytical research results of two precast insulation mortar concrete sandwich panels (PIMSP) and two precast concrete composite panels as one-way slabs under bending load. Obtaining a prefabricated floor slab that can balance thermal insulation and structural performance can reduce material consumption and increase inter-story usage height. As the sandwich material for PIMSP, insulation mortar with a strength of 6 MPa was used. Truss-shaped shear connectors were used for shear force transfer. Then, finite element analysis was used to analyze and study the unidirectional flat plate model. The results showed that the tested PIMSP achieved a complete composite effect in the elastic stage and a semi-composite effect in the plastic stage. The PIMSP crack pattern resembles that of a precast concrete slab when utilized as a one-way slab. The load transfer capacity of truss-shaped shear connectors is relatively small, and it is mainly used as a connection between floors. Experiments have demonstrated that PIMSP panels can serve as a structural substitute for regular concrete floors in residential buildings.

Shear performance of X and Z configuration wythe ties for insulated precast concrete sandwich panels using different FRP materials

This study investigates Insulated Precast Concrete Sandwich Panels (PCSP), a versatile system integrating structural and thermal efficiencies suitable for diverse structures. PCSP's structural behavior depends on effective shear force transfer between two wythes through components known as "Wythe Ties." Testing twelve push-off specimens explores angled connectors with various FRP-composite Wythe Tie configurations to assess stiffness in PCSP design. Serving as the second phase of experimental work after prior findings' publication, the research compares Steel, Carbon, and Basalt FRP wythe tie behaviors, analyzing key factors' influence on strength, stiffness, and deformability. Evaluation includes performance assessments of shear strength, relative slip, stiffness, and failure modes. To validate, a nonlinear 3D-FE analysis simulates tested specimens' behavior, revealing a fitting progressive failure pattern and demonstrate good agreement with experimental results. The study unveils significant shear tie variations in PCSPs, where type and configuration impact ultimate capacity, stiffness, and toughness of wythe ties. Notably, Notably, for X-configuration shear ties, steel and CFRP-bar shear ties were observed to be the most effective material types. On the other hand, for Z-configuration shear ties, CFRP-Strip and CFRP-bar shear ties were identified as the most effective material types. Overall, these insights guide designers in choosing suitable wythe tie configurations and materials for specific PCSP applications.

Generic and simplified approaches for the structural analysis of precast concrete sandwich panels

This paper presents a comparison between three numerical models developed for the structural analysis of composite precast concrete sandwich panels under lateral loading. The first model is based on a full finite element analysis where “slip” between the layers is obtained from the elastic deformability of the various components. The second model is based on a simplified finite element analysis where the effect of the shear connectors is smeared and modeled through an effective shear stiffness of the insulation layer. The third approach provides closed-form expressions for evaluating the deflection and is based on the classical sandwich beam theory where the shear connectors are considered through the effective stiffness of the insulation, similar to the second model. The structural response obtained from the three models was compared for various panel configurations and good correlation was obtained. A reasonable agreement with test results from the literature was also demonstrated. Therefore, both the simplified finite element model and the classical sandwich beam theory (closed-form solution) are recommended for the elastic structural analysis and for estimating the degree of composite action at the serviceability limit state of precast concrete sandwich panels.

Study of the flexural performance and a novel calculation formula for the degree of composite action for precast concrete sandwich panels

SummaryThis study investigates the flexural performance and degree of composite action (DCA) of precast concrete sandwich panels (PCSPs) with four types of connectors. Five full‐scale specimens were designed, and 4‐point bending tests were performed. The specimens included four PCSPs utilizing glass fiber reinforced polymer (GFRP) truss connectors, steel truss connectors, concrete rib connectors, and GFRP pin connectors, respectively, along with a solid panel (SP). The results indicated that the flexural performance and DCA provided by the four types of connectors followed an ascending order as follows: GFRP pin‐type connectors, GFRP truss connectors, steel truss connectors, and concrete rib‐type connectors. Moreover, the study presented a novel method for calculating DCA, namely, the neutral axis method, which was compared with the displacement and strain methods. The reasonableness and accuracy of the neutral axis method in calculating DCA during the linear elastic stage were verified. Results indicated that the neutral axis method provided more precise and reasonable DCA that closely matched the experimental results compared with the displacement and strain methods. Additionally, the neutral axis method was simpler to calculate DCA and had a broader range of applications. Finally, the study provided recommendations for the optimal application scenarios of each calculation method.

Experimental analysis on the out-of-plane structural performance of single-face superposed shear walls with different horizontal connections

Single-face superposed (SFS) shear wall is a novel precast concrete sandwich panel (PCSP) wall that can be used as load-bearing walls in high-rise buildings and underground structures in seismic zones. This paper investigates the out-of-plane structural performance of SFS shear walls with different horizontal connections. Three SFS shear walls with different lap-spliced rebar connection configurations at the horizontal connections were designed and tested to compare their out-of-plane structural performance with that of a cast-in-place specimen, in terms of failure modes, cracking patterns, load-displacement curves, stiffness degradation curves, ductility, and force transfer mechanism of lap-spliced rebar connections. The test results showed that the SFS shear wall specimens exhibited and maintained a high level of composite action until failure, and the studied three different horizontal connections can allow effective force transfer between the upper shear walls and the lower. The stiffness, ductility, and ultimate bearing capacities of SFS shear walls under out-of-plane monotonic loading were significantly higher than those of cast-in-place shear walls. The bearing capacity was found to depend to a large extent on the location of additional vertical connecting rebar, the displacement mainly caused by rigid body rotation and related to crack width at joint. A calculation method of the ultimate bearing capacity of a SFS shear wall under out-of-plane horizontal loads was proposed. Finally, some suggestions on the setting of the vertical connecting bar are put forward.

Flexural performance of novel ECC-RC composite sandwich panels

To address the shortcomings of precast concrete sandwich panels (PCSPs) such as insufficient load-bearing capacity, poor ductility behavior, and susceptibility to cracking under temperature stress, this study reinforced the face layer of PCSP with engineered cementitious composite (ECC), resulting in the development of novel ECC-RC composite sandwich panels (ECSPs). The flexural performance of ECSP was revealed by way of a four-point bending test and finite element analysis. Test results showed that incorporating ECC into the wythes substantially improved the flexural performance of PCSP, and the maximum crack width of ECSP was well below the corresponding limit requirement when the mid-span deformation reached the serviceability limit state of the panel. ECSP presented a long load-hardening phase owing to the excellent tensile toughness of ECC, and the properties of the reinforcement could be fully utilized in ECSP without causing “over reinforced” damage as seen in PCSP. Finite element analysis demonstrated that the initial cracks of ECSP did not occur at the tensile edge of the panel, indicating excellent durability of ECSP. Based on the test results and finite element analysis, a formula for the flexural carrying capacity of ECSP was proposed, and the corresponding calculation model demonstrated better applicability. It is recommended to use 20 mm thick ECC to reinforce the face layer of ECSP for optimal economic benefits in practical engineering, while paying attention to the interface problem between ECC and concrete.

Holistic analysis for the efficiency of the thermal mass performance of precast concrete panels in hot climate zones

PurposeThis paper investigates thermal mass performance (TMP) in hot climates. The impact of using precast concrete (PC) as a core envelope with different insulation materials has been studied. The aim is to find the effect of building mass with different weights on indoor energy consumption, specifically cooling load in hot climates.Design/methodology/approachThis research adopted a case study and simulation methods to find out the efficiency of different mass performances in hot and humid climate conditions. Different scenarios of light, moderate and heavyweight mass using PC have been developed and simulated. The impact of these scenarios on indoor cooling load has been investigated using the integrated environment solution-virtual environment (IES-VE) software.FindingsThe results showed that adopting a moderate weight mass of two PC sheets and a cavity layer in between can reduce indoor air temperature by 1.17 °C; however, this type of mass may increase the cooling demand. On the other hand, it has been proven that adopting a heavyweight mass for building envelopes and increasing the insulation material has a significant impact on reducing the cooling load. Using a PC Sandwich panel and increasing the insulation material layers for external walls and thickness by 50 mm will reduce the cooling load by 15.8%. Therefore, the heavyweight mass is more efficient compared to lightweight and moderate mass in hot, humid climate areas such as the UAE, in spite of the positive indoor TMP that can be provided by the lightweight mass in reducing the indoor air temperature in the summer season.Originality/valueThis research contributes to the thermal mass concept as one of these strategies that have recently been adopted to optimize the thermal performance of buildings and developments. Efficient TMP can have a massive impact on reducing energy consumption. However, less work has investigated TMP in hot and humid climate conditions. Furthermore, the impact of the PC on indoor thermal performance within hot climate areas has not been studied yet. The findings of this study on TMP in the summer season can be generated in all hot climate zones, and investigating the TMP in other seasons can be extended in future studies.

Shear Transfer Mechanism between CFRP Grid and EPS Rigid Foam Insulation of Precast Concrete Sandwich Panels

An experimental program was implemented to investigate the shear transfer mechanism of carbon-fiber-reinforced polymer (CFRP) grids and expanded polystyrene (EPS) rigid foam insulation in three wythe precast concrete sandwich wall panels. The purpose of the research was to measure the shear flow capacity and to observe the failure mode(s) of precast concrete sandwich panels manufactured with a CFRP grid shear transfer mechanism between wythes. Six precast concrete sandwich panels were examined by push-out tests in which the center concrete wythe was pushed downward with respect to two outer concrete wythes. It was observed that the average shear flow capacity of the specimens having 2 in (51 mm) thick foam was higher than that of the specimens having 4 in (102 mm) thick foam. In addition, stiffness decreased significantly when the thickness of the EPS insulation increased. The failure mode for the panels included relative displacement between the center concrete wythe and the outer concrete wythes. Test results showed that panels tended to fail by CFRP grid rupture, CFRP grid pull-out, and loss of bond at the concrete/foam interface. Further tests should be performed to fully comprehend the nature of the shear transfer mechanism between the specific CFRP grid used and EPS rigid foam insulation.

Shaking table tests and seismic assessment of a full-scale precast concrete sandwich wall panel structure with bolt connections

A novel, light-weight, sustainable, repairable and cost-effective precast concrete sandwich wall panel structure system is proposed in this paper, including the dry bolt connections and the precast concrete sandwich panels. To evaluate the seismic performance of precast structure system, a sequence of shaking table tests is carried on the full-scale precast concrete sandwich wall panel structure, and the dynamic characteristics, damage pattern, dynamic responses and seismic fragility are investigated and analyzed by the test results under service level earthquake, design based earthquake, and maximum considered earthquake. The seismic fragility curves and failure probability curves are analyzed by the shaking table test results, which quantitatively describes the seismic performanceexpressed by probability. The results show that the precast concrete sandwich wall panel structure performs high lateral stiffness, large safety margins and high strength reserves. The precast concrete sandwich wall panel structure system presents a good seismic performance. The damage of the structure is slight under maximum considered earthquakes, and the structure has begun to enter the plastic stage. The light-weight characteristic reduces the dynamic responses, and the mild sliding between precast components consumes a fraction of seismic energy.

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Study on impact resistance of precast light-weight concrete sandwich panels

To investigate the dynamic impact resistance of precast lightweight sandwich panels (PLCSP) composed of non-sintered coal ash ceramsite concrete and self-developed thermal blocking shear connectors, drop hammer impact tests with different impact energy were carried out in the central area of the exterior wythe. The dynamic response of PLCSP under different steel fibers content, wythe thickness, and the different number of shear connectors was compared and analyzed. The numerical simulation was carried out by LS-DYNA. The results show that 2% volume fraction of steel fibers enhance the stiffness of the panel by improving the overall impact toughness, while the increase in wythe thickness slows down the panel amplitude to enhance the stiffness. The exterior wythe of the PLCSP has penetrated failure, and the failure mode of the interior wythe changes from bending failure to collapse failure with the increase of the number of shear connectors. Therefore, the arrangement spacing of shear connectors can be appropriately reduced to reduce the risk of collapse failure. The ratio of maximum displacement and residual displacement of the panel under different impact energies ranged from 3.37 to 5.94, and the maximum erosion depth of the hammer was twice the displacement of the bottom of the panel, indicating that the unique sandwich structure and material of the PLCSP have good impact resistance. The research results can provide reference for the design and application of PLCSP.